Satgen37 13th Dec 89 L and S band feed, Pacsat Aerials Many thanks for your comments and questions A simple homebrew 1.2 to 2GHz feed . Several questions on this topic. I built a feed for a 1.8m F/D 0.5 dish from two tin cans , each 13.8 cms diam and 16.2 cms long. They are soldered end to end, with the bottom cut out of the one nearest the dish. Linear feed is via an N type socket mounted 6cms from the closed end furthest from the dish. From this socket an adjustable screw projects about 3.5 cms inside the tin. The N type connects via a very short piece of coax to an F type plug connected to a Connexions SA20 900 to 17500 Mhz pre amp ( a standard sat tv type) with 18v fed to it up the coax from a home brew power supply/splitter, which connects to the R7000 receiver or the analyser. L and S band test targets for the above are firstly the Sun, which I used to adjust the position of this tin can feed in a strong lightweight collar. Noting that you can adjust the feed so its shadow is central on the dish and peak the radio signal. Other targets are Meteosat 1686.8, 1691.0, 1694.5, Az about 178. Inmarsat many channels roughly every 50Khz from 1537.5 to 1542.4 , at about azimuth 216, and the low earth orbit NOAAs near 1700 MHz with fierce doppler shift and tracking rates. Pacsat aerials. Continuing tests with simple widebeam reception 70 cm aerials are producing useful results from Polar bear 435.974 MHz on morning orbits up to 1400 ut and evening orbits after 2100 ut. Useful signals are possible even on the polar passes where Polar Bear skirts my northern horizon. Nothing has been heard of UFO 432.881 since 8th Nov 89. Aerials.Comments on queries. The G3RUH 70cms helix gets very good reports. Uosat 2 has a beacon on 435.025 MHz but it is not on continuously ( use Polar Bear for tests ). Oscar 13 reception on 2m needs at least a 5XY aerial and good preamp, but for consistent results use a 10 XY. Computer control of aerials. Automatic tracking programs are available from Amsat UK . BUT do not expect too much of them . They are only as good as the weak link in the system = aerial rotator. Most aerial rotators use simple " Angle to turn produces drive signal ". These are first order servos called bang bang servos in the trade because they either go, or do not go. They are very inaccurate on continuous short movements . They suffer serious "Stiction" = static friction ,push necessary to get them moving, problems. You can buy very expensive systems with 2nd and 3rd order control but they are not really worth it. What you need for say pacsat is something that is nearly there most of the time, provided your aerial is wide beam and you carefully align it to minise difference in run in from clockwise versus anticlockwise. You may get a shock when you do that sort of test . My present set up has a nearly constant 3 degree error difference on run ins from opposite directions. In addition to the above please remember that most aerials squint, their mechanical alignment is not the same as their electrical alignment. Ground aerial squint is best checked on a slow moving target like AO13. ( note this is not SQUINT ANGLE, that is a feature of SAT aerial pointing) 73 de John GM4IHJ@GB7SNE